Before you book for October, study well the patterns of something called "The South Asian Monsoon." At that time of the year you might be pushing the South Asian Monsoon envelope. That monsoon there is different from mine. Still, look into it, studying up on what you really want to see, ie currently, when and where is the best time to dive with whale sharks if you are into that, and line it up. It is a very, very ancient ocean so it is awesome. And, I got the impression that you might have dived it before, yet might not have. This sea has sea snakes in it in case the idea freaks you out. I am hoping you have dived before in waters where they were, if not, I cannot really coach you on that on the internet.